This invention relates to an improved wick for absorbing molten solder.
It is fairly common in the electronics industry to remove solder from a printed circuit board. This may be needed, for example, when a component has been removed and is to be replaced by a different component. The old solder may be removed to assure a reliable joint. For many years now solder has been removed by placing a copper braid on the solder and touching it with a hot soldering iron. Typically, the braid has a thin coating of flux and when the solder melts, it is drawn into the braid by capillary action.
Braid for desoldering is shown, for example, in U.S. Pat. Nos. 3,627,191, 3,726,464 and 3,715,797. In each of these, fine wires of copper or the like are braided together in the form of a tube. The tube is flattened to make a braided ribbon. In a braided ribbon, the wires all extend in the longitudinal direction along the tube. The individual wires are in rather close engagement, yielding a ribbon with a limited volume between wires within which solder may be drawn.
Technicians using the braid may therefore press on the end of the braid to cause it to buckle and open up additional void space. This, however, causes the ribbon to become wider, which may be undesirable in close spaces. An exemplary ribbon is only two or three millimeters wide, although wider ribbons may be used in some applications.
The tightness of the braid was recognized in U.S. Pat. No. 4,416,408 (Reissue No. 32,086) by Spirig, who illustrates an exemplary braided wire in FIG. 1. When the braid is buckled, as mentioned above, it does not form a fan as illustrated in the patent, but instead remains braided and simply becomes wider and more open. Spirig proposes knitting a desoldering wick with a strand of copper in a continuous helically-forming knitting machine to form a tubular open mesh structure which is subsequently flattened. Spirig states that although the illustrated wick is formed by knitting, "it might instead be formed by crocheting or alternatively an open mesh structure might be formed by weaving or indeed by braiding, providing the adjacent strands will not be contiguous and will instead provide open spaces for absorbing the molten solder". How adjacent strands can be non-contiguous is not explained.
Despite these teachings from more than a decade ago, a satisfactory desoldering wick has not been made by any technique except braiding. The reason for this is not known, but it may be a matter of economics, or it may not be feasible to make a satisfactory wick by knitting. A knit wick may be too open to soak up an adequate amount of solder.
It is desirable, therefore, to produce a desoldering wick which can be made economically and reliably, which can absorb more solder than conventional braid, and which can absorb solder more quickly.